build: add docker support

[zaventh]

Adds support for running in a container which is useful in cloud GPU providers.

I am happy to modify the README as well but I didn't want to be too presumptuous.

[s3inlc]

Thank you for your input and contribution regarding a docker build for the agent binary. Due to the way the agent updates itself if there is a new version from the server, the agent should be built into the zip and running as this instead of directly from the code. Even if the zip then gets reset on a re-creation of the container, it would avoid that the agent could be stuck in an endless update loop.

I created a similar docker support but building a zip first and then include this into the agent in the PR #61